Prenatal Cannabinoid Exposure Elicits Memory Deficits Associated with Reduced PSA-NCAM Expression, Altered Glutamatergic Signaling, and Adaptations in Hippocampal Synaptic Plasticity

Cannabis is now one of the most commonly used illicit substances among pregnant women. This is particularly concerning since developmental exposure to cannabinoids can elicit enduring neurofunctional and cognitive alterations. This study investigates the mechanisms of learning and memory deficits resulting from prenatal cannabinoid exposure (PCE) in adolescent offspring. The synthetic cannabinoid agonist WIN55,212-2 was administered to pregnant rats, and a series of behavioral, electrophysiological, and immunochemical studies were performed to identify potential mechanisms of memory deficits in the adolescent offspring. Hippocampal-dependent memory deficits in adolescent PCE animals were associated with decreased long-term potentiation (LTP) and enhanced long-term depression (LTD) at hippocampal Schaffer collateral-CA1 synapses, as well as an imbalance between GluN2A- and GluN2B-mediated signaling. Moreover, PCE reduced gene and protein expression of neural cell adhesion molecule (NCAM) and polysialylated-NCAM (PSA-NCAM), which are critical for GluN2A and GluN2B signaling balance. Administration of exogenous PSA abrogated the LTP deficits observed in PCE animals, suggesting PSA mediated alterations in GluN2A- and GluN2B- signaling pathways may be responsible for the impaired hippocampal synaptic plasticity resulting from PCE. These findings enhance our current understanding of how PCE affects memory and how this process can be manipulated for future therapeutic purposes.

What does family involvement in care provision look like across hospital settings in Bangladesh, Indonesia, and South Korea?

BACKGROUND

Family members provide care whilst staying in the patient's room across a range of cultural settings, irrespective of resource availability in many Asian countries. This has been reported as a contributing factor to the spread of several outbreaks, including COVID-19. Despite these reports, very little is known about the risk of healthcare-associated infection (HAI) transmission related to the involvement of family and private carers in the clinical setting. As a starting point to understanding this issue, this study aimed to provide insights regarding the patient care activities undertaken by family and private carers and the guidance provided to these carers around infection control measures in hospitals located in Bangladesh, Indonesia, and South Korea.

METHOD

A qualitative study involving 57 semi-structured interviews was undertaken in five tertiary level hospitals across the selected countries. Two groups of individuals were interviewed: (1) patients and their family carers and private carers; and (2) healthcare workers, including doctors, nurses, hospital managers and staff members. Drawing upon the principles of grounded theory, an inductive approach to data analysis using thematic analysis was adopted.

RESULTS

Five main themes were generated from the analysis of the data: (1) expectation of family carers staying with a patient; (2) residing in the patient's environment: (3) caring activities undertaken by family carers; (4) supporting and educating family carers and (5) communication around healthcare-associated infection and infection prevention and control.

CONCLUSION

Based on the types of activities being undertaken, coupled with the length of time family and private carers are residing within the clinical setting, coupled with an apparent lack of guidance being given around IPC, more needs to be done to ensure that these carers are not being inadvertently exposed to HAI's or other occupational risks.

OP0129 BELIMUMAB AFTER RITUXIMAB SIGNIFICANTLY REDUCED IGG ANTI-DSDNA ANTIBODY LEVELS AND PROLONGED TIME TO SEVERE FLARE IN PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS

Background:

B cell depletion with rituximab, an anti-CD20 mAb, has shown efficacy for systemic lupus erythematosus (SLE) in open-label studies but failed to meet primary endpoints in two randomised, placebo controlled trials. Rituximab increases BAFF levels which has been associated with subsequent lupus flares. We hypothesised that high BAFF levels after rituximab limit its effectiveness in SLE and that the anti-BAFF monoclonal antibody belimumab given immediately after rituximab could be a valuable therapeutic strategy.

Objectives:

To assess the safety and obtain preliminary evidence for efficacy of belimumab following rituximab therapy in patients with SLE.

Methods:

BEAT-LUPUS (Belimumab after B cell depletion in SLE) is a 52-week phase IIb, randomised, double-blind, placebo-controlled clinical trial investigating the safety and efficacy of intravenous belimumab after B cell depletion therapy (rituximab). The maximum permissible prednisolone dose throughout the trial was 20mg/day with encouragement to reduce by 50% from baseline by 6 months. The primary outcome measure was log IgG anti-dsDNA antibody serum levels at 52 weeks measured by ELISA. A linear regression ANCOVA model was fitted to evaluate the difference in 52-week anti-dsDNA levels between treatment arms adjusting for anti-dsDNA value at screening (before rituximab) and randomisation (4-8 weeks after the 1st infusion of rituximab), CD19 > or < 0.01x109/l at randomisation, and renal involvement at screen. Secondary outcomes included measures of disease activity and incidence of adverse events. B cell (CD19) counts were measured by flow cytometry. Intention to treat analysis was adopted. Full ethical and regulatory approval was obtained. A comprehensive description of the protocol and statistical analysis plan is available(1,2).

Results:

52 patients with active SLE received rituximab (2 infusions, 2 weeks apart) and then randomised to receive either belimumab (n=26) or placebo (n=26) 4-8 weeks after their 1st dose of rituximab. 32 patients completed trial treatment protocol (belimumab or placebo) through to 52 weeks, withdrawals were equally split between belimumab and placebo. There was a significant reduction in IgG anti-dsDNA antibody levels in patients treated with belimumab compared to placebo at 52 weeks (p<0.001, Figure 1); 43 patients were included in the intention to treat analysis at 52 weeks.

Figure 1.

Serum IgG anti-dsDNA antibody levels (geometric means with 95% confidence intervals) in patients treated with rituximab, then randomised to belimumab or placebo at 1st trial infusion. An intention to treat linear regression ANCOVA model was fitted to evaluate the difference in 52-week anti-dsDNA between belimumab or placebo adjusting for baseline values and stratification factors. N= patient numbers who provided serum samples at time indicated.

Kaplan-Meier curves demonstrated that belimumab reduced the risk of severe flare (BILAG A flare) compared to placebo (hazard ratio 0.27, 95% confidence interval 0.07-0.97, unadjusted log-rank p=0.03). There were 10 and 3 severe flares in the placebo and belimumab group respectively. There was no difference in cumulative steroid dose over the course of the trial between belimumab and placebo.

Belimumab did not increase the incidence of infections, serious or total adverse events, nor withdrawals due to adverse events compared to placebo. Belimumab significantly suppressed B cell repopulation at 52 weeks compared to placebo (p=0.001), but not total serum IgG.

Conclusion:

This placebo controlled double blind trial met its primary endpoint, a significant reduction in IgG anti-dsDNA antibody levels, and demonstrated that belimumab prolongs the time to severe flare compared to placebo. These results suggest that belimumab after rituximab is a safe and effective treatment for patients with SLE and supports further development of this combination as a novel therapeutic strategy.

References:

[1]Jones A, et al. BMJ Open. 2019;9:e032569.

[3]Muller P, et al. Trials. 2020;21:652.

Acknowledgements:

We acknowledge the important contribution of the BEAT Lupus Trial Steering Committee, the Data Monitoring Committee, the BEAT-LUPUS trial investigators, and all the patients participating in the trial or involved in its development.

Funding:

This trial was supported by Versus Arthritis (grant number 20873) and the UCLH Biomedical Research Centre (BRC). GSK provided belimumab free of charge, as well as additional funding.

GSK had no role in the design of this study and will not have any role during its execution, analyses, interpretation of the data, or decision to submit results. Versus Arthritis and the UCLH BRC reviewed the relevant grant proposals and monitor progress of relevant aspects of the study but did not play any role in the analyses, interpretation of data, or decision to submit results.

Disclosure of Interests:

Muhammad Shipa: None declared, Andrew Embleton-Thirsk: None declared, Mariea Parvaz: None declared, Liliana Santos Ribeiro: None declared, Patrick Muller: None declared, Kashfia Chowdhury: None declared, David Isenberg Speakers bureau: Paid by GSK to deliver educational talks, Consultant of: Received consultancy fees from GSK for attending advisory boards, Caroline Doré: None declared, Caroline Gordon Speakers bureau: Paid for educational speaker role by GSK, Consultant of: Received consultancy fees from GSK for attending advisory boards, Michael Ehrenstein Speakers bureau: Paid by GSK as a speaker in educational sessions, Consultant of: Received consultancy fees from GSK for attending advisory boards, Grant/research support from: GSK provided part of the funding for the BEAT-LUPUS trial

Electric field encephalography for brain activity monitoring

OBJECTIVE

We describe an early-stage prototype of a new wireless electrophysiological sensor system, called NeuroDot, which can measure neuroelectric potentials and fields at the scalp in a new modality called Electric Field Encephalography (EFEG). We aim to establish the physical validity of the EFEG modality, and examine some of its properties and relative merits compared to EEG.

APPROACH

We designed a wireless neuroelectric measurement device based on the Texas Instrument ADS1299 Analog Front End platform and a sensor montage, using custom electrodes, to simultaneously measure EFEG and spatially averaged EEG over a localized patch of the scalp (2 cm  ×  2 cm). The signal properties of each modality were compared across tests of noise floor, Berger effect, steady-state visually evoked potential (ssVEP), signal-to-noise ratio (SNR), and others. In order to compare EFEG to EEG modalities in the frequency domain, we use a novel technique to compute spectral power densities and derive narrow-band SNR estimates for ssVEP signals. A simple binary choice brain-computer-interface (BCI) concept based on ssVEP is evaluated. Also, we present examples of high quality recording of transient Visually Evoked Potentials and Fields (tVEPF) that could be used for neurological studies.

MAIN RESULTS

We demonstrate the capability of the NeuroDot system to record high quality EEG signals comparable to some recent clinical and research grade systems on the market. We show that the locally-referenced EFEG metric is resistant to certain types of movement artifacts. In some ssVEP based measurements, the EFEG modality shows promising results, demonstrating superior signal to noise ratios than the same recording processed as an analogous EEG signal. We show that by using EFEG based ssVEP SNR estimates to perform a binary classification in a model BCI, the optimal information transfer rate (ITR) can be raised from 15 to 30 bits per minute-though these preliminary results are likely sensitive to inter-subject variations and choice of scalp locations, so require further investigation.

SIGNIFICANCE

Enhancement of ssVEP SNR using EFEG has the potential to improve visually based BCIs and diagnostic paradigms. The time domain analysis of tVEPF signals shows robust features in the electric field components that might have clinical relevance beyond classical VEP approaches.

Sexual dimorphism of AMBRA1-related autistic features in human and mouse

Ambra1 is linked to autophagy and neurodevelopment. Heterozygous Ambra1 deficiency induces autism-like behavior in a sexually dimorphic manner. Extraordinarily, autistic features are seen in female mice only, combined with stronger Ambra1 protein reduction in brain compared to males. However, significance of AMBRA1 for autistic phenotypes in humans and, apart from behavior, for other autism-typical features, namely early brain enlargement or increased seizure propensity, has remained unexplored. Here we show in two independent human samples that a single normal AMBRA1 genotype, the intronic SNP rs3802890-AA, is associated with autistic features in women, who also display lower AMBRA1 mRNA expression in peripheral blood mononuclear cells relative to female GG carriers. Located within a non-coding RNA, likely relevant for mRNA and protein interaction, rs3802890 (A versus G allele) may affect its stability through modification of folding, as predicted by in silico analysis. Searching for further autism-relevant characteristics in Ambra1^+/- mice, we observe reduced interest of female but not male mutants regarding pheromone signals of the respective other gender in the social intellicage set-up. Moreover, altered pentylentetrazol-induced seizure propensity, an in vivo readout of neuronal excitation-inhibition dysbalance, becomes obvious exclusively in female mutants. Magnetic resonance imaging reveals mild prepubertal brain enlargement in both genders, uncoupling enhanced brain dimensions from the primarily female expression of all other autistic phenotypes investigated here. These data support a role of AMBRA1/Ambra1 partial loss-of-function genotypes for female autistic traits. Moreover, they suggest Ambra1 heterozygous mice as a novel multifaceted and construct-valid genetic mouse model for female autism.

A Girl with Ulcerative Colitis in a Tertiary Care Hospital- a Case Report

Ulcerative colitis (UC) is a chronic idiopathic inflammatory disorder of colon. We are presenting a case of ulcerative colitis in a 12 yrs old girl who presented with passage of loose bloody stool, low grade intermittent fever, abdominal pain with tenesmus and arthralgia of large joint along with significant wt loss. Diagnosis was confirmed by colonoscopy and biopsy. Treatment was thereafter started with parenteral steroid initially then oral steroid and meselamine. The patient is now on remission and is on regular follow up. DOI: http://dx.doi.org/10.3329/pulse.v6i1-2.20352 Pulse Vol.6 January-December 2013 p.53-56

Observational assessment and correlates to blood pressure of future physicians of Bengal

INTRODUCTION

Hypertension is a modern day epidemic and growing public health problem. A sizable proportion of world populations suffer from prehypertension or hypertension.

OBJECTIVES

The present study was carried out to detect the prevalence of undiagnosed hypertension among undergraduate medical students and to identify the associated risk factors.

MATERIALS AND METHODS

The study was observational in nature and was done in medical colleges of Bengal. Study tool was a predesigned, pretested, validated, and semi-structured questionnaire containing both open-ended and close-ended questions. Data were collected through self-administration, clinical, and anthropometric examination. The data were then tabulated, analyzed and interpretation was done by using percentage and Chi-square test.

RESULTS

Most of the students (63%) were young adults, predominantly males (67%) and day scholars (71%). Almost one-third of them either suffered from hypertension or at risk of hypertension. Hypertension was found higher among male students. Family history of hypertension or diabetes mellitus was not associated with hypertension. Vegetarian or nonvegetarian diet or extra-salt consumption was also not associated with hypertension. Smoking was shown positively associated with hypertension but alcohol consumption was not. Higher per capita monthly income and overweight or obesity were shown positively associated with hypertension.

CONCLUSION

The overall prevalence of hypertension in this study was 13% and there were positive association of hypertension with multiple socio-demographic factors like age, sex, type of family, per capita monthly income, residence, BMI, smoking, etc.

Ab initio structure determination of cytochrome c6 by combined reciprocal space-real space approach

The direct method program SAYTAN has been applied successfully to redetermine the structure of cytochrome c6, a heme-containing redox protein with 89 amino acids, a Fe atom and 151 solvent water molecules in the asymmetric unit and data to 1.1 Å resolution. The crystal system is rhombohedral with space group R3, cell parameters a = b = c = 40.43(10) Å, α = β = γ = 80.25(5)°. Starting with initially random phases, useful phase sets could be obtained from multiple trials of direct methods based on reciprocal space. The E-map corresponding to the phase set with the lowest mean phase error, 45.4°, showed a distorted octahedral coordination around the Fe site. The phase estimates from the metal atom and a few neighbouring atoms in the initial E-map have been improved by density modification procedure (PERP) operating in direct space. The resulting electron density map can be interpreted readily by an automated procedure to build up the protein structure.

Resorbable plate fixation in pediatric craniofacial surgery: long-term outcome

OBJECTIVE

To determine the long-term efficacy of resorbable plate fixation in pediatric patients undergoing craniofacial surgery for congenital anomalies, traumatic deformities, or skull base tumors.

DESIGN

Retrospective case review.

MATERIALS AND METHODS

Medical records of 57 consecutive cases using resorbable plates and screws for craniofacial fixation in patients younger than 18 years were analyzed.

MAIN OUTCOME MEASURES

The status of bone healing postoperatively (anatomical union, malunion, delayed union, or nonunion) and any complications or adverse effects (hardware visibility or palpability, plate extrusion, or infection) were noted.

RESULTS

In midfacial and upper face procedures (54 patients) anatomical union and uncomplicated bone healing occurred in 52 (96%) of the patients. In this same group, complications (plate extrusion) occurred in 2 patients (3.7%) and were resolved using conservative treatment without untoward sequelae. These outcomes are comparable to results using metal osteosynthesis in similar situations. Costs of resorbable hardware are similar to existing metal fixation systems.

CONCLUSIONS

Our data support the use of bioresorbable plate fixation in pediatric craniofacial surgery as a means of avoiding the potential and well-documented problems with rigid metal fixation. Indications include fractures and segmental repositioning in low-stress non-load-bearing areas of the middle and upper craniofacial skeleton. Although there is an initial learning curve in using this technology, we believe the benefits are well worth the effort and represent a major advance in pediatric craniofacial surgery.

Mice deficient for spermatid perinuclear RNA-binding protein show neurologic, spermatogenic, and sperm morphological abnormalities

Spermatid perinuclear RNA-binding protein (SPNR) is a microtubule-associated RNA-binding protein that localizes to the manchette in developing spermatids. The Spnr mRNA is expressed at high levels in testis, ovary, and brain and is present in these tissues in multiple forms. We have generated a gene trap allele of the murine Spnr, named Spnr(+/GT). Spnr(GT/GT) mutants show a high rate of mortality, reduced weight, and an abnormal clutching reflex. In addition to minor anatomical abnormalities in the brain, males exhibit defects in spermatogenesis that include a thin seminiferous epithelium and disorganization of spermatogenesis. Most of the sperm from mutant males display defects in the flagellum and consequently show decreased motility and transport within the oviducts. Furthermore, sperm from mutant males achieve in vitro fertilization less frequently. Our findings suggest that SPNR plays an important role in normal spermatogenesis and sperm function. Thus, the Spnr(GT/GT) mutant male mouse provides a unique model for some human male infertility cases.

Pax4 regulatory elements mediate beta cell specific expression in the pancreas

Pax4 is a member of the Pax (Pax, paired box) family of transcription factors with restricted expression and essential functions in the developing pancreas. Pax4 deficient mice do not develop pancreatic beta and delta cells and thus die after birth due to diabetes. In this study using transgenic mouse technology we report the identification and characterization of a 0.9 kb DNA fragment in the 5'-region of the gene, which by itself is able to direct Pax4 expression in the endocrine pancreas, recapitulating the beta-cell-specific in vivo expression pattern of Pax4. The 0.9 kb DNA fragment contains an area spanning 407 base pairs that is highly conserved between human and mouse showing 88% identity. This promoter region contains sequence motifs that have been shown to be involved in beta-cell-specific expression of insulin, Pdx1 and islet amyloid polypeptide (IAPP). In addition, we determined a previously undescribed 5'intron.

A new gene trap construct enriching for insertion events near the 5' end of genes

The gene trap approach is based on the integration of a gene trap vector into the genome. This can be done either by electroporation of a plasmid construct or by infection with a viral vector. Commonly used viral gene trap vectors have been shown to select for integrations near the 5' end of genes. To date, no plasmid vector with a similar tendency has been reported. In this paper we describe a new plasmid vector, pKC199beta geo. This vector contained a short splice acceptor fragment from the Hoxc9 gene, a full length lacZ gene, including an ATG, and a reduced activity, mutant neomycin phosphotransferase gene as a selectable marker. This vector enriched the population of trapped genes in our gene trap screen for insertion events in the 5' end of genes. In the two cases examined the beta-galactosidase activity pattern accurately reflected the endogenous promotor activity.

A unique loop in the DNA-binding crevice of bacteriophage T7 DNA polymerase influences primer utilization

The three-dimensional structure of bacteriophage T7 DNA polymerase reveals the presence of a loop of 4 aa (residues 401-404) within the DNA-binding groove; this loop is not present in other members of the DNA polymerase I family. A genetically altered T7 DNA polymerase, T7 polDelta401-404, lacking these residues, has been characterized biochemically. The polymerase activity of T7 polDelta401-404 on primed M13 single-stranded DNA template is one-third of the wild-type enzyme and has a 3'-to-5' exonuclease activity indistinguishable from that of wild-type T7 DNA polymerase. T7 polDelta401-404 polymerizes nucleotides processively on a primed M13 single-stranded DNA template. T7 DNA polymerase cannot initiate de novo DNA synthesis; it requires tetraribonucleotides synthesized by the primase activity of the T7 gene 4 protein to serve as primers. T7 primase-dependent DNA synthesis on single-stranded DNA is 3- to 6-fold less with T7 polDelta401-404 compared with the wild-type enzyme. Furthermore, the altered polymerase is defective (10-fold) in its ability to use preformed tetraribonucleotides to initiate DNA synthesis in the presence of gene 4 protein. The location of the loop places it in precisely the position to interact with the tetraribonucleotide primer and, presumably, with the T7 gene 4 primase. Gene 4 protein also provides helicase activity for the replication of duplex DNA. T7 polDelta401-404 and T7 gene 4 protein catalyze strand-displacement DNA synthesis at nearly the same rate as does wild-type polymerase and T7 gene 4 protein, suggesting that the coupling of helicase and polymerase activities is unaffected.

Perinatal lethality of microtubule-associated protein 1B-deficient mice expressing alternative isoforms of the protein at low levels

Microtubule-associated protein 1B (MAP1B) has been implicated in axogenesis in cultured cells. To gain insight into the functions that MAP1B plays in vivo, we analyzed a strain of Map1B mutant mice generated by a gene trapping approach. Homozygous mice die on the first day after birth, probably due to a severe abnormal development of the nervous system. They present alterations in the structure of several brain regions. The normal Map1B gene yields different protein isoforms from alternatively spliced transcripts. The smaller isoforms were present in wild type, hetero-, and homozygous mice, but their expression was higher in the mutants than in the wild-type. Moreover, trace amounts of MAP1B protein were also observed in Map1B homozygous mutants, indicating an alternative splicing around the gene trap insertion. Thus, the Map1B gene trapped mutation reported in this work did not generated a null mutant, but a mouse with a drastic deficiency in MAP1B expression. Analyses of these mice indicate the presence of several neural defects and suggest the participation of MAP1B in neuronal migration.

Le Fort I osteotomy and skull base tumors: a pediatric experience

BACKGROUND

The Le Fort I maxillary osteotomy approach for skull base tumor removal in the pediatric age group has not been widely discussed in the literature except for sporadic case reports and limited case series.

OBJECTIVES

To review our experience with the Le Fort I osteotomy and to propose that it be used as an alternative approach because of its many advantages for the removal of tumors of the central skull base and paranasal sinuses.

DESIGN

Case series.

SETTING

Tertiary academic center.

PATIENTS AND METHODS

A 5-year retrospective chart review of cases involving children who had undergone skull base tumor resection via the Le Fort I osteotomy approach.

INTERVENTIONS

Skull base tumor removal via the Le Fort I osteotomy approach.

MAIN OUTCOME MEASURES

Tumor type, location, and size; intraoperative and postoperative complications; and residual tumor and/or tumor recurrence associated with the surgical approach.

RESULTS

Eleven patients (9 boys and 2 girls; mean age, 14.3 years) were identified through the chart review. The tumor types included 8 angiofibromas, 1 malignant fibrous histiocytoma, 1 giant cell tumor, and 1 cavernous hemangioma. All these lesions had extensive tumor growth into at least 1 of the following sites: pterygomaxillary space, sphenoidal sinus, and areas adjacent to the optic nerve, cavernous sinus, clivus, and anterior cranial fossa. The mean follow-up for this cohort was 12.8 months. No intraoperative complications were noted. Postoperative complications were reviewed with respect to the approach. To date, there have been no cases of residual tumor or tumor recurrence that can be attributed to the procedure.

CONCLUSIONS

Our experience suggests that the Le Fort I osteotomy approach is a useful technique for the removal of extensive central skull base tumors and paranasal sinuses in the pediatric age group. It has distinct advantages over traditional anterior or lateral approaches, including a more direct line of vision and improved exposure and cosmesis.

Querkopf, a MYST family histone acetyltransferase, is required for normal cerebral cortex development

In order to find, and mutate, novel genes required for regulation of neurogenesis in the cerebral cortex, we performed a genetic screen in mice. As the result of this screen, we created a new mouse mutant, querkopf. The querkopf mutation is due to an insertion into a MYST family histone acetyltransferase gene. Mice homozygous for the querkopf mutation have craniofacial abnormalities, fail to thrive in the postnatal period and have defects in central nervous system development. The defects in central nervous system development are particularly prominent in the cerebral cortex, which is disproportionally smaller than in wild-type mice. A large reduction in the size of the cortical plate was already apparent during embryogenesis. Homozygous mice show a lack of large pyramidal cells in layer V of the cortex, which is reflected in a reduction in the number of Otx1-positive neurons in this layer during postnatal development. Homozygous mice also show a reduction in the number of GAD67-positive interneurons throughout the cortex. Our results suggest that Querkopf is an essential component of a genetic cascade regulating cell differentiation in the cortex, probably acting in a multiprotein complex regulating chromatin structure during transcription.

Valine of the YVDD motif of moloney murine leukemia virus reverse transcriptase: role in the fidelity of DNA synthesis

The YXDD motif is highly conserved in the reverse transcriptase family. The variable X residue is occupied by valine and methionine in MuLV RT and HIV-1 RT, respectively. Previous studies have shown that Tyr 222, the Y residue of the YXDD motif in MuLV RT, constitutes a major component of the fidelity center of the enzyme [Kaushik, N., Singh, K., Alluru, I., and Modak, M. J. (1999) Biochemistry 38, 2617-2627]. In this work, we present evidence that reverse transcriptases containing valine in the "X" position of the YXDD motif generally catalyze DNA synthesis with greater fidelity than those containing methionine or alanine. In the MuLV RT system, the two mutants V223M and V223A exhibited an overall reduced fidelity of DNA synthesis, specifically for RNA-templated reactions. Further analysis revealed that these mutants exhibit a higher efficiency of misinsertion on MS2 RNA than the wild-type enzyme for every mispair tested. However, unlike HIV-1 RT, the insensitivity of the wild-type MuLV RT to all four ddNTPs remained unchanged by mutation of V223 to Met or Ala. A 3D molecular model of the ternary complex of MuLV RT, template primer, and dNTP suggests that Val 223 along with its neighboring Tyr 222 stabilizes the substrate binding pocket via hydrophobic interactions with the dNTP substrate and template-primer.

Identification of a novel mouse Iroquois homeobox gene, Irx5, and chromosomal localisation of all members of the mouse Iroquois gene family

The Drosophila genes of the Iroquois-Complex encode homeodomain containing transcription factors that positively regulate the activity of certain proneural Achaete/Scute-C (AS-C) genes during the formation of external sensory organs (J. L. Gomez-Skarmeta and J. Modolell, EMBO J 17:181-190, 1996). Previously, we have identified three highly-related genes of the mouse Iroquois gene family that exert specific expression patterns in the central nervous system (A. Bosse et al., Mech Dev 69:169-181, 1997). In the present paper, we report the identification of a novel member of the Iroquois gene family, Irx5, that shows a restricted spatio/temporal expression during early mouse embryogenesis, distinct from the expression of Irx1-3. An extensive sequence analysis of 20 Iroquois-like genes from seven organisms reveals a high conservation of the homeodomain. Phylogenetic tree reconstruction showed a clustering of the members of the Iroquois gene family into groups of orthologous genes. Together, with the data obtained from the chromosomal mapping analysis, the results indicate that these genes have appeared in vertebrates during evolution as a result of gene duplication.

The motif D loop of human immunodeficiency virus type 1 reverse transcriptase is critical for nucleoside 5'-triphosphate selectivity

Human immunodeficiency virus type 1 reverse transcriptase (RT) has limited homology with DNA and RNA polymerases. The conserved Lys-220 of motif D is a signature of RNA-dependent polymerases. Motif D is located in the "palm" domain and forms a small loop from Thr-215 to Lys-223. This loop is absent from the polymerase I family of DNA-dependent polymerases. Analysis of RT structures in comparison with other polymerases reveals that the motif D loop has the potential to undergo a conformational change upon binding a nucleotide. We find that amino acid changes in motif D affect the interaction of RT with the incoming nucleotide. A chimeric RT in which the loop of motif D is substituted by the corresponding amino acid segment from Taq DNA polymerase lacking this loop has a decreased affinity for incoming nucleotides. We have also constructed a mutant RT where the conserved lysine at position 220 within the motif D is substituted with glutamine. Both RT(K220Q) and the chimeric RT are resistant in vitro to 3'-deoxy 3'-azidothymidine 5'-triphosphate (AZTTP). These results suggest that motif D is interacting with the incoming nucleotide and a determinant of the sensitivity of reverse transcriptases to AZTTP. We do not observe any interaction of motif D with the template primer.

Juvenile nasopharyngeal angiofibroma

This is a retrospective study of 17 patients with juvenile nasopharyngeal angiofibroma treated from 1983 to 1996. Patients with Stage I or II disease according to the Fisch classification system were treated surgically by a transpalatal approach. One patient underwent a Le Fort I osteotomy and down-fracture approach for access. Three patients underwent combined transpalatal and lateral rhinotomy for access, whereas one underwent a transcervical double mandibular osteotomy to facilitate the exposure. A patient with Stage IV disease underwent a combined subcranial frontonasal osteotomy plus a Le Fort I osteotomy for access to a massive angiofibroma. Initial surgical management prevented recurrence in 79% of patients. Two patients with intracranial extension were treated with primary irradiation therapy; their tumours became asymptomatic. Preoperative angiography and embolization were used to treat all surgical candidates. The use of newer craniofacial or subcranial techniques and infratemporal fossa approaches with osteotomies can provide access to large angiofibromas even when there is skull base or intracranial involvement. Surgical exposure may also be enhanced by the use of the Le Fort I osteotomy and down-fracture approaches.

Primary amyloidosis presenting as massive cervical lymphadenopathy with severe dyspnea: a case report and review of the literature

Amyloidosis is an end point of several diseases in which the unifying characteristic is the association and extracellular deposition of the insoluble protein fibrils within various tissues and organs. We have discussed a variety of clinical findings of primary amyloidosis with emphasis on its otolaryngologic manifestations. This case represents the second report in the literature of a neck mass resulting from a plasma cell dyscrasia and the first report of AL disease producing such extensive cervical lymphadenopathy as to cause significant respiratory compromise.

Prox1 function is crucial for mouse lens-fibre elongation

Although insights have emerged regarding genes controlling the early stages of eye formation, little is known about lens-fibre differentiation and elongation. The expression pattern of the Prox1 homeobox gene suggests it has a role in a variety of embryonic tissues, including lens. To analyse the requirement for Prox1 during mammalian development, we inactivated the locus in mice. Homozygous Prox1-null mice die at mid-gestation from multiple developmental defects; here we describe the specific effect on lens development. Prox1 inactivation causes abnormal cellular proliferation, downregulated expression of the cell-cycle inhibitors Cdkn1b (also known as p27KIP1) and Cdkn1c (also known as p57KIP2), misexpression of E-cadherin and inappropriate apoptosis. Consequently, mutant lens cells fail to polarize and elongate properly, resulting in a hollow lens. Our data provide evidence that the progression of terminal fibre differentiation and elongation is dependent on Prox1 activity during lens development.

Distinct cis-essential modules direct the time-space pattern of the Pax6 gene activity

Pax6 is a regulatory gene with restricted expression and essential functions in the developing eye and pancreas and distinct domains of the CNS. In this study we report the identification of three conserved transcription start sites (P0, P1, alpha) in the murine Pax6 locus. Furthermore, using transgenic mouse technology we localized independent cis-regulatory elements controlling the tissue-specific expression of Pax6. Specifically, a 107-bp enhancer and a 1.1-kb sequence within the 4.6-kb untranslated region upstream of exon 0 are required to mediate Pax6 expression in the lens, cornea, lacrimal gland, conjunctiva, or pancreas, respectively. Another 530-bp enhancer fragment located downstream of the Pax6 translational start site is required for expression in the neural retina, the pigment layer of the retina, and the iris. Finally, a 5-kb fragment located between the promoters P0 and P1 can mediate expression into the dorsal telencephalon, the hindbrain, and the spinal cord. The identified Pax6/cis-essential elements are highly conserved in pufferfish, mouse, and human DNA and contain binding sites for several transcription factors indicative of the cascade of control events. Corresponding regulatory elements from pufferfish are able to mimic the reporter expression in transgenic mice. Thus, the results indicate a structural and functional conservation of the Pax6 regulatory elements in the vertebrate genome.

Efficient gene trap screening for novel developmental genes using IRES beta geo vector and in vitro preselection

We have used different gene trap vectors and in vitro preselection of embryonic stem (ES) cells for a large scale screening of insertional mutations in developmentally regulated genes. A gene trap vector was constructed, which contains an internal ribosome entry site (IRES) upstream from a betageo selectable-reporter fusion gene. Analysis of 801 independent integrations revealed that the IRESbetageo vector allows for a global enrichment of about 15 folds in the number of detectable gene trap events when compared with a conventional betageo vector. Characterization of in vitro and in vivo lacZ expression suggested that this IRES-based vector is able to capture a wide range of genes expressed in a variety of tissues and developmental stages, and it can also allow trapping of genes expressed at very low levels in ES cells. A preselection protocol was devised, where gene-trapped ES cells were grown in the presence of specific growth/differentiation factors such as follistatin, nerve growth factor, and retinoic acid. Several gene trap integrations were found to be either activated or repressed by one of these factors. Characterization of lacZ expression during embryogenesis showed a strong enrichment of restricted patterns in vivo after ES cell preselection. These results suggest that a combination of IRESbetageo vector and in vitro preselection is more effective for the capture and mutation of a large number of developmental genes.

Genes expressed after retinoic acid-mediated differentiation of embryoid bodies are likely to be expressed during embryo development

In order to test if retinoic acid-mediated differentiation of embryoid bodies can be used as an in vitro preselection method for ES cell lines generated by gene trap, we correlated gene expression after in vitro differentiation and in 11.5-day embryos. Fifty-two genes captured by gene trap and expressed in undifferentiated embryonic stem cells were analyzed. Most genes expressed after differentiation in vitro were also expressed during embryo development. In order to correlate the expression patterns in vitro and in vivo, the in vitro expression in the center and in the periphery of the embryoid body outgrowths was observed. This allowed us to distinguish, according to in vitro expression, not expressed genes from those expressed widely in 11.5-day embryos. Consequently, with this parameter we increased the probability to obtain the restricted expression patterns in vivo. This study demonstrates the potential of the differentiation procedure in combination with the gene trap to select in vitro for genes expressed during embryo development.

Gene trap expression and mutational analysis for genes involved in the development of the mammalian nervous system

We have used a large-scale gene trap approach for the isolation and mutation of genes that might play roles in the developing nervous system. After in vitro integration of two different gene trap vectors (pGT1.8geo: Skarnes et al. [1995] Proc. Natl. Acad. Sci. USA 92:6592-6596; IRES beta geo: Chowdhury et al. [1997] Nucleic Acids Res. 25:1531-1536) in mouse embryonic stem (ES) cell lines, we created 64 transgenic mouse lines. The expression analysis of the reporter gene during embryogenesis of heterozygous embryos revealed 47 lines with a variety of patterns. Around one-third (36%) of these gene trap lines showed spatiotemporal expression that was either restricted predominantly in the developing nervous system (11 lines; 17%) or widespread but with very high levels of expression in the nervous tissue (12 lines; 19%). In most cases, a correlation was found between the in vitro and the in vivo patterns of the reporter gene expression. Thus far, preliminary mutant analysis of 16 gene trap lines with potentially interesting expression patterns in the developing nervous system showed that mice homozygous for eight (50%) insertions were lethal, whereas the homozygous mice from five gene trap lines (31%) showed a lower than expected Mendelian ratio of live homozygous animals. Analysis of beta-galactosidase reporter gene expression during embryogenesis has shown that four transgenic lines are useful lacZ in situ markers for specific regions of the developing nervous system. Here, we discuss some in vivo and in vitro selection criteria that may increase the number of the trapped genes potentially involved in the control of neural development and some future strategies to improve further the efficiency of the gene trap approach.

Follicular cells of the thyroid gland require Pax8 gene function

The thyroid gland develops from two distinct embryonic lineages: follicular cells (which produce thyroxine) and parafollicular C-cells (which produce calcitonin) are of endodermal and neural crest origin, respectively. Little is known about the molecular mechanisms governing the generation of these different cell types. Mice lacking the transcription factor Ttf1 lack both cell types and thus are unable to develop a thyroid gland. By analysis of Pax8-/- mice, we demonstrate that Pax8 is required for the formation of the follicular cells in the thyroid. We present evidence that Pax8 is necessary for providing cues for the differentiation of competent endoderm primordia into thyroxin-producing follicular cells.

Pax6 is required for differentiation of glucagon-producing alpha-cells in mouse pancreas

The functional unit of the endocrine pancreas is the islet of Langerhans. Islets are nested within the exocrine tissue of the pancreas and are composed of alpha-, beta-, delta- and gamma-cells. beta-Cells produce insulin and form the core of the islet, whereas alpha-, delta- and gamma-cells are arranged at the periphery of the islet and secrete glucagon, somatostatin and a pancreatic polypeptide, respectively. Little is known about the molecular and genetic factors regulating the lineage of the different endocrine cells. Pancreas development is known to be abolished in Pdx1-mutant mice and Pax4 mutants lack insulin-producing beta-cells. Here we show that the paired-box gene Pax6 is expressed during the early stages of pancreatic development and in mature endocrine cells. The pancreas of Pax6 homozygous mutant mice lack glucagon-producing cells, suggesting that Pax6 is essential for the differentiation of alpha-cells. As mice lacking Pax4 and Pax6 fail to develop any mature endocrine cells, we conclude that both Pax genes are required for endocrine fate in the pancreas.

Evidence for the stochastic integration of gene trap vectors into the mouse germline

A large scale insertional mutagenesis experiment was performed in embryonic stem (ES) cells by introducing two types of gene trap vectors into the genome. These cell lines carrying mutations were introduced into the mouse germline. In order to assess the feasibility of a large scale cloning of the targeted genes from these lines, we have isolated and characterized 55 trapped exons from the corresponding ES cells. Analysis of the data has revealed that vectors containing or lacking an internal ribosome entry site (IRES) can integrate into the ES cell genome stochastically. The targeted genes comprise 30% known genes, 20% expressed sequence tags (ESTs) and 50% novel or unknown genes. The known genes belong to several major classes and represent complete or partial knockouts. Using currently available methods or modifications of them, it should be feasible to do a large scale cloning of trapped genes from the mouse ES cell lines.

The Pax4 gene is essential for differentiation of insulin-producing beta cells in the mammalian pancreas

The mammalian pancreas contains two distinct cell populations: endocrine cells which secrete hormones into the bloodstream, and exocrine cells, which secrete enzymes into the digestive tract. The four endocrine cell types found in the adult pancreas-(alpha, beta, delta and PP-synthesize glucagon, insulin, somatostatin and pancreatic polypeptide, respectively. All of these endocrine cells arise from common multipotent precursors, which coexpress several hormones when they start to differentiate. Expression of some homeobox genes in the early developing pancreas has been reported. The Pax4 gene is expressed in the early pancreas, but is later restricted to beta cells. Inactivation of Pax4 by homologous recombination results in the absence of mature insulin- and somatostatin-producing cells (beta and delta, respectively) in the pancreas of Pax4 homozygous mutant mice, but glucagon-producing alpha cells are present in considerably higher numbers. We propose that the early expression of Pax4 in a subset of endocrine progenitors is essential for the differentiation of the beta and delta cell lineages. A default pathway would explain the elevated number of alpha cells in the absence of Pax4.

An alpha-E-catenin gene trap mutation defines its function in preimplantation development

Catenins are proteins associated with the cytoplasmic domain of cadherins, a family of transmembrane cell adhesion molecules. The cadherin-catenin adhesion system is involved in morphogenesis during development and in the maintenance of the integrity of different tissue types. Using a gene trap strategy, we have isolated a mouse mutation for the gene encoding the alpha-E-catenin. This form of the alpha-catenin appears frequently coexpressed with E-cadherin in epithelial cell types. The mutation obtained eliminates the carboxyl-terminal third of the protein but nevertheless provokes a complete loss-of-function phenotype. Homozygous mutants show disruption of the trophoblast epithelium (the first differentiated embryonic tissue), and development is consequently blocked at the blastocyst stage. This phenotype parallels the defects observed in E-cadherin mutant embryos. Our results show the requirement of the alpha-E-catenin carboxy terminus for its function and represent evidence of the role of the alpha-E-catenin in vivo, identifying this molecule as the natural partner of the E-cadherin in trophoblast epithelium.

Elucidation of the role of Arg 110 of murine leukemia virus reverse transcriptase in the catalytic mechanism: biochemical characterization of its mutant enzymes

Based on the projected three-dimensional equivalence of conserved amino acids in the catalytic domains of DNA polymerases, we propose Arg 110 of MuLV RT to be an important participant in the catalytic mechanism of MuLV RT. In order to obtain evidence to support this proposition and to assess the functional importance of Arg 110, we carried out site directed mutagenesis of Arg 110 and replaced it with Lys, Ala, and Glu. The mutant enzymes were characterized with respect to their kinetic parameters, ability to bind template-primers, and the mode of DNA synthesis. All the three substitutions at 110 position resulted in severe loss of polymerase activity without any significant effect on the RNase H function. In spite of an approximately 1000-fold reduction in kcat of polymerase activity with three mutant enzymes, no significant reduction in the affinities for either template-primer or dNTP substrates was apparent. Mutant enzymes also did not exhibit significant sulfur elemental effect, implying that the chemical step, i.e., phosphodiester bond formation, was not defective. Examination of the mode of DNA synthesis by the mutant enzymes indicated a shift from processive to the distributive mode of synthesis. The mutants of R110 also displayed significant loss of pyrophosphorolysis activity. Furthermore, the time course of primer extension with mutant enzymes indicated severe reduction in the rates of addition of the first nucleotide and even further reduction in the addition of the second nucleotide. These results suggest that the rate limiting step for the mutant enzymes may be before and after the phosphodiester bond formation. Based on these results, we propose that Arg 110 of MuLV RT participates in the conformational change steps prior to and after the chemical step of polymerase reaction.

Diagnosis and treatment of intracranial complications of paranasal sinus infections

Complications and local extension of paranasal sinus infections most often involve the orbit and periorbita. Because of the widespread use of antibiotics since World War II, intracranial extension of maxillofacial sinusitis is rarely seen today. Nevertheless, the clinician must be aware of the potential for these complications, because late recognition of this condition and delays in treatment can increase morbidity and mortality rates. A comprehensive, current review of sinogenic intracranial complications is presented, with illustrative cases of brain abscess, subdural empyema, meningitis, cavernous sinus thrombosis, epidural abscess, and osteomyelitis. The mechanisms and potential for intracranial spread of infection from the frontal, sphenoid, and ethmoid sinuses are discussed in detail. The management of each type of complication is outlined, including the use of computed tomography and magnetic resonance imaging, and the role of surgical drainage.

Segment-specific expression of the neuronatin gene during early hindbrain development

The developing hindbrain is segmented in a series of repetitive bulges called neuromeres or rhombomeres. In the mouse, first molecular evidence for segmentation of the hindbrain came from rhombomeres 3- and 5-specific expression of the Krox-20 gene. The hindbrain segments are linked with the expression of different Hox genes which have a role in patterning the hindbrain and branchial region of the vertebrate head. Here we identified by subtractive hybridization a gene, mouse neuronatin, that is downregulated in P19 embryo carcinoma cells that have undergone a partial differentiation process. Neuronatin encodes putative transmembrane proteins of 54, 55, and 81 amino acids that might serve as protein ligands, cofactors, or small cell adhesion molecules. The neuronatin gene is transiently expressed in rhombomeres 3 and 5 during early hindbrain development and in the floor of the foregut pocket. In addition, expression is observed in the early Rathke's pouch, in the derived adenohypophysis, and in the developing inner ear. During later embryogenesis the neuronatin gene is strongly expressed in the major part of the central and peripheral nervous system. These results suggest that neuronatin participates in the maintenance of segment identity in the hindbrain and pituitary development and maturation or maintenance of the overall structure of the nervous system.

Development and evaluation of rapid monoclonal antibody-based coagglutination test for direct detection of Vibrio cholerae O139 synonym Bengal in stool samples

A monoclonal antibody-based coagglutination test directly detected Vibrio cholerae O139 synonym Bengal in 83 of 120 watery diarrheal stool specimens; on culture, 90 samples were positive. Thus, with 92% sensitivity, 100% specificity, and 100% positive and 95% negative predictive values, the coagglutination test is a useful rapid test for V. cholerae O139.

Regulated expression of Brachyury(T), Nkx1.1 and Pax genes in embryoid bodies

Embryonic stem cells (ES) can be exploited to analyze in vitro mechanisms of cellular differentiation. We have utilized ES-derived embryoid body formation in an attempt to study cell types resulting from in vitro differentiation. To this end, a variety of molecular markers, preferably those which have been associated with regulatory events during mouse embryogenesis, was employed. Specifically, Brachyury (T), Pax-3 and Pax-6 genes as well as Nkx-1.1 were used. We could demonstrate that the expression of these genes in vitro was regulated by growth factors such as activin A or bFGF. Implications of these findings and the possible applications for identifying new genes are discussed.

Glutamate induces the growth factors NGF, bFGF, the receptor FGF-R1 and c-fos mRNA expression in rat astrocyte culture

The effect of glutamate on primary cultures of rat cortical astrocytes was studied using Northern blot hybridization. Incubation with glutamate (100 microM, 15 min) induced nerve growth factor (NGF), basic fibroblast growth factor (bFGF), FGF receptor (FGF-R1) and proto-oncogene c-fos gene expression in a time dependent manner. Maximal induction of NGF, bFGF and FGF-R1 mRNA was reached after 4 h of incubation (7.2-fold induction of NGF, 3-fold increase in bFGF and 3.6-fold induction of FGF-R1 mRNA). The induction kinetics of NGF, bFGF and FGF-R1 mRNA are similar. The rapid (1 h) 77-fold induction of the c-fos transcript precedes the induction of the other genes tested.

The ubiquitous transactivator Zfp-38 is upregulated during spermatogenesis with differential transcription

We describe the complete nucleotide sequence of a full length cDNA clone encoding a new mouse zinc finger protein gene, Zfp-38 and localize it on chromosome 5 by the interspecific backcross analysis. The N-terminal domain of the Zfp-38 protein (64 kDa) contains 358 amino acids and the C-terminal domain of 197 residues encodes 7 zinc fingers. We also present evidence that Zfp-38 is a strong transcriptional activator. The transactivation domain was localized in the non finger region and a fusion protein containing 112 amino acid residues from this region of the Zfp-38 and the DNA binding domain of the yeast Gal 4 protein, very efficiently transactivated the expression of a reporter CAT plasmid, harboring the Gal4 target site. By in situ hybridization and northern blotting technique, the Zfp-38 transcript can be detected at a highly elevated level during spermatogenesis. Its expression accompanies the progression from pachytene spermatocytes to round spermatids. The undifferentiated spermatogonia or the haploid elongated spermatid and the spermatozoa do not show any detectable level of the transcript. Interestingly, other tissues express low levels of a slightly shorter transcript with a different 5' end as determined by RNase protection. The presence of both a transcriptional activating domain and 7 DNA binding zinc fingers, coupled with the cell type(s) specific expression pattern, suggests that Zfp-38 has the potential to regulate transcription during spermatogenesis.

Classification and treatment of zygomatic fractures: a review of 1,025 cases

The treatment of zygomatic fractures varies among surgeons, and the cosmetic and functional results are frequently less than optimal. A treatment guideline based on a simple classification of zygomatic fractures is presented. The emphasis is placed on the indications for closed and open reduction, consistent methods of three-dimensional alignment and fixation, and the management of concomitant infraorbital rim and orbital floor fractures. Postoperative results with regard to infraorbital nerve and maxillary sinus dysfunction, malar asymmetry, and orbital complications in the treatment of 1,025 consecutive zygomatic fractures are presented.

Free radicals induce gene expression of NGF and bFGF in rat astrocyte culture

Hydrogen peroxide (H2O2) is a type of active oxygen species produced mainly in blood by inflammation, ischemia or anoxia. Treatment of rat neonatal cortical astrocytes in culture with 0.2-1.0 mM H2O2 which is lethal for hippocampal neurons, increases nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) mRNA content in a time dependent manner. H2O2 also increases c-fos mRNA expression, which is probably involved in the gene regulation of both NGF and bFGF. Maximal induction was reached after 6 h of incubation (5.7-fold increase in NGF and 2.4-fold induction of bFGF mRNA). Hydrogen peroxide induced bFGF and NGF gene expression suggests that neurotrophic factors in astrocytes could be induced by lesion, consistent with their protective function in the CNS.

Treatment of 813 zygoma-lateral orbital complex fractures. New aspects

A 10-year experience with surgical treatment of 813 zygomalateral orbital complex fractures is reviewed. Regardless of the type or severity of the fracture pattern, concomitant fractures of the orbital floor and rim were approached exclusively through the transconjunctival approach without a lateral canthotomy. The advantages of this approach compared with the subciliary access are the avoidance of a visible scar and markedly reduced incidence of postoperative lower eyelid complications such as ectropion and edema. Implants of lyophilized dura or cartilage and autogenous bone were used to reconstruct orbital floor defects. Malar asymmetry is a frequent complication of zygoma fractures resulting from inadequate three-dimensional reduction. Methods for accurate reduction and stabilization, indications for closed and open reduction, and management of the fractured infraorbital rim are emphasized. The indications for miniplates vs wire ligatures for the infraorbital rim are discussed. Long-term follow up and evaluation of the results with regard to the fracture pattern, complications, maxillary sinus dysfunction, and facial and orbital symmetry are presented.

One step 'miniprep' method for the isolation of plasmid DNA

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Zinc finger protein gene complexes on mouse chromosomes 8 and 11

Two murine homologs of the Drosophila Krüppel gene, a member of the gap class of developmental control genes that encode a protein with zinc fingers, were mapped to mouse chromosomes 8 and 11 by using somatic cell hybrids and an interspecific backcross. Surprisingly, both genes were closely linked to two previously mapped, Krüppel-related zinc finger protein genes, suggesting that they are part of gene complexes.

Pax8, a murine paired box gene expressed in the developing excretory system and thyroid gland

Several mouse genes designated 'Pax genes' contain a highly conserved DNA sequence homologous to the paired box of Drosophila. Here we describe the isolation of Pax8, a novel paired box containing clone from an 8.5 day p.c. mouse embryo cDNA library. An open reading frame of 457 amino acids (aa) contains the 128 aa paired domain near the amino terminus. Another conserved region present in some other paired box genes, the octapeptide Tyr-Ser-Ile-Asn-Gly-Leu-Leu-Gly, is located 43 aa C-terminal to the paired domain. Using an interspecies backcross system, we have mapped the Pax8 gene within the proximal portion of mouse chromosome 2 in a close linkage to the surf locus. Several developmental mutations are located in this region. In situ hybridization was used to determine the pattern of Pax8 expression during mouse embryogenesis. Pax8 is expressed transiently between 11.5 and 12.5 days of gestation along the rostrocaudal axis extending from the myelencephalon throughout the length of the neural tube, predominantly in two parallel regions on either side of the basal plate. We also detected Pax8 expression in the developing thyroid gland beginning at 10.5 days of gestation, during the thyroid evagination. In the mesonephros and metanephros the expression of Pax8 was localized to the mesenchymal condensations, which are induced by the nephric duct and ureter, respectively. These condensations develop to functional units, the nephrons, of the kidney. These data are consistent with a role for Pax8 in the induction of kidney epithelium. The embryonic expression pattern of Pax8 is compared with that of Pax2, another recently described paired box gene expressed in the developing excretory system.